The catalytic function of the gephyrin-binding protein IQSEC3 regulates neurotransmitter-specific matching of pre- and post-synaptic structures in primary hippocampal cultures

Autor: Shiva K. Tyagarajan, Giovanna Bosshard, Benjamin F. N. Campbell, Jean-Marc Fritschy, Simon Früh
Přispěvatelé: University of Zurich, Fritschy, Jean-Marc
Rok vydání: 2018
Předmět:
0301 basic medicine
1303 Biochemistry
Calmodulin
Primary Cell Culture
Presynaptic Terminals
2804 Cellular and Molecular Neuroscience
10050 Institute of Pharmacology and Toxicology
610 Medicine & health
Hippocampus
Biochemistry
Catalysis
03 medical and health sciences
Cellular and Molecular Neuroscience
Glutamatergic
0302 clinical medicine
Pregnancy
Image Processing
Computer-Assisted
Animals
Guanine Nucleotide Exchange Factors
Rats
Wistar
gamma-Aminobutyric Acid
Neurons
Neurotransmitter Agents
Gephyrin
biology
ADP-Ribosylation Factors
Chemistry
GABAA receptor
Binding protein
Post-Synaptic Density
Rats
Cell biology
Apposition
030104 developmental biology
ADP-Ribosylation Factor 6
Synapses
biology.protein
570 Life sciences
GABAergic
Calcium
Female
Postsynaptic density
030217 neurology & neurosurgery
Zdroj: Journal of Neurochemistry. 147:477-494
ISSN: 0022-3042
Popis: In dissociated neuronal cultures the absence of spatial and temporal cues causes the emergence of mismatched synapses, where post-synaptic proteins of GABAergic synapses are in part apposed to glutamatergic pre-synaptic terminals and vice versa. This mismatch offers an opportunity to study the mechanisms that regulate correct apposition of pre- and post-synaptic elements. We report here that the IQ motif and Sec7 domain-containing protein 3 (IQSEC3; BRAG3; synArfGEF) specifically regulates the mislocalization of GABAergic post-synaptic density (PSD) proteins. Over-expression of IQSEC3 constructs harboring mutations that ablate Sec7 domain or IQ motif function revealed that IQSEC3 catalytic activity is involved in the control of apposition between the GABAergic PSD and glutamatergic terminals. Neurons co-expressing eGFP-gephyrin with IQSEC3 Sec7 mutant displayed a drastically increased fraction of mismatched eGFP-gephyrin clusters compared to other IQSEC3 constructs. Along with eGFP-gephyrin, endogenous GABAA receptor cluster mismatching was increased by IQSEC3 Sec7 mutant over-expression. Conversely, GFP-PSD-95 clusters were unaffected by over-expression of any IQSEC3 construct. The GABAergic PSD mismatch phenotype was recapitulated by Arf6 dominant-negative mutant over-expression, suggesting that Arf6 activation by IQSEC3 is an essential step in this pathway. In addition, we provide biochemical evidence to confirm gephyrin/IQSEC3 interaction near the IQSEC3 IQ motif, which in turn binds calmodulin at low Ca2+ concentrations. Taken together, our findings identify a post-synaptic protein which specifically regulates correct apposition of the GABAergic PSD to pre-synaptic terminals.
Databáze: OpenAIRE
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